Engine failure at 30,000 feet forced the emergency landing of a Southwest Airlines jet on Tuesday, leading to the death of one passenger and injuries to seven others. The fatality was the first aboard a U.S. flight since 2009, according to the National Transportation Safety Board.
Baltimore/Washington International Thurgood Marshall Airport is a Southwest hub — the airline is responsible for about 70 percent of the flights to and from the airport — and all its planes are 737s, most with the same kind of engine that failed.
If you're flying Southwest, here's what you need to know:
1. What happened? (And what's "metal fatigue"?)
The engine failed while the plane was on its way from New York to Dallas, and shrapnel smashed a window and damaged the fuselage, killing a passenger and injuring seven others, authorities said. The passenger who died was identified as Jennifer Riordan, a Wells Fargo executive of Albuquerque, N.M. The seven others were treated for minor injuries.
NTSB investigators said one of that engine's fan blades broke off from the hub during the flight. The broken edge of the blade showed crack lines consistent with "metal fatigue," according to the NTSB.
Flying Magazine reports that metal fatigue refers to metal parts that undergo many repeated strains, eventually failing at a level of stress far below what they originally were able to handle.
"Events of this kind are rare — fewer than three percent of aircraft accidents involve structural failures, and only a fraction of those involve fatigue," the magazine reported in a 2005 explainer. "But we have seen a number of them, including several bursting Boeings, and their psychological impact is tremendous."
2. Is the 737 safe?
An NTSB investigation of Tuesday's incident is underway, but the 737 is considered the "workhorse" for the passenger travel industry and Southwest. It is the bestselling jetliner in the world and has a good safety record, the AP reports.
Southwest said Wednesday that it would speed up its existing inspection program of all its CFM56 engines after Tuesday's incident.
"The accelerated inspections are being performed out of an abundance of caution and are expected to be completed over the next 30 days," the airline said in a statement. "The accelerated checks are ultrasonic inspections of fan blades of the CFM56 engines."
The engines are designed to contain broken pieces to prevent them from piercing the fuselage. It's unclear why that didn't happen Tuesday. At least two other U.S. commercial airliners have experienced engine failures in the last two years, but neither resulted in injuries.
Despite this incident, commercial airline travel remains vastly safer than other methods of transportation. Since the last American commercial airline fatality, more than 200,000 people have died in car crashes in the U.S.
3. What does Southwest say?
In addition to the announcement that it would speed up inspections, Southwest pledged to support the victims in a statement:
"We are deeply saddened to confirm that there is one fatality resulting from this accident," Southwest's statement said. "The entire Southwest Airlines Family is devastated and extends its deepest, heartfelt sympathy to the Customers, employees, family members and loved ones affected by this tragic event. We have activated our emergency response team and are deploying every resource to support those affected by this tragedy."
Southwest CEO Gary Kelly expressed confidence in the company's fleet of 737s after the incident. "The airplane in my opinion is proven. It's very reliable," he said, according to USA Today. "It has the greatest success of any aircraft type over a long, long period of time. It doesn't create any doubt in my mind, at least at this point."
4. What do federal safety regulators say?
NTSB chairman Robert Sumwalt said one of the engine's fan blades was separated and missing, and he confirmed the fatality on the flight on Wednesday. The formal investigation is expected to last 12 to 15 months.
The investigation is focusing on whether wear and tear caused a fan blade to snap off, the Associated Press reported.
When investigators from the NTSB examined the broken engine in Philadelphia just hours after its emergency landing, they immediately saw that one of the left engine's 24 fan blades was missing.
"This fan blade was broken right at the hub, and our preliminary examination of this was there is evidence of metal fatigue where the blade separated," NTSB chairman Robert Sumwalt said.
5. Is Boeing worried?
The Seattle-based airplane manufacturer has sent a technical team to assist the NTSB in its investigation, but it hasn't released much additional information.
"Boeing extends its deepest condolences to the family of the passenger who passed away as a result of today's incident on SWA Flight 1380," the Boeing statement said.
"Our thoughts are with all of the passengers and crew who were on board the flight and with the entire Southwest Airlines family. A Boeing technical team is providing assistance at the request and under the direction of the U.S. National Transportation Safety Board as the agency conducts its investigation."